This invention relates to electrical wiring devices such as plugs and connectors.
Wiring devices frequently have cord grips to restrain cords whose conductors are connected to contact terminals in the device. The cord grips are generally characterized by a plurality of flexible fingers hinged proximate the outer periphery of the base of the device. The fingers bear against the cord and are held tightly in place upon assembly of a cover element with the base. Examples of the foregoing are contained in Smith U.S. Pat. No. 3,437,980, Apr. 8, 1969 and McLaughlin et al. U.S. Pat. No. 4,304,455, Dec. 8, 1981.
Despite the number and variety of previous cord grips and their general success, there is a need for further alternative and improved arrangements of cord grips in wiring devices for reliable retention of a cord and prevention of the entry of dirt and the like. Devices with those characteristics should desirably be economical both to manufacture and use with a single device accommodating cords of varying sizes.
The invention achieves these purposes in a wiring device of a molded plastic plug or connector body and a molded plastic cover or housing. The cover has an opening through which a conductor is inserted to be wired to terminals in the body. The body has a plurality, such as two, integrally molded extensions or grip fingers designed to restrain the conductor, or the grip fingers may be on a separate molded part, such as a ring, adjacent the body. Assembly screws for joining the body and cover draw them together and apply an inward force on the grip fingers via a cam surface or ramp. The grip fingers restrict the conductor from movement when the assembly screws attain a specific torque level. A key feature of the combination of the invention is that the grip fingers are hinged longitudinally through the center of their individual contact surfaces and can flex to conform to diameters of varied conductor sizes. The grip fingers engage a greater surface area and close off more of the cover opening as compared to previous devices. The ramp surface within the cover serves a two-fold purpose. It applies a force to the grip fingers that restricts the conductor from pulling out and a force that conforms the grip fingers to the diameter of the conductor. Additional aspects of the invention will be discussed in connection with the preferred embodiments hereinafter.